Digitalis extraction



Patented Dec. 19, 1950 UNITED STATES PATENT ()F'FICE No Drawing. Application June 23, 1949, Serial-No. 100,959

8 Claims. (Cl. 260210.5)

The'pres'ent invention'relates to a novel process of isolating digitalis glycosides from plant material containing the same.

The present applicationis a continuation-inpart of my copending application Serial No. 719,931 filed January?. 1947, now Patent No. 2,500,173, entitled Extraction of Digitalis Glycosides.

"According to the'ab'o'veidentified application, it wasfound possible to extract the active glycosides of digitalis by means of an aqueous solution. According to that process the fresh plant material was subjected to disintegration for the purpose of rupturing all or nearly all of the plant cells. This disintegration was followed by an extraction of the disintegrated plant material with water and resulted in the production of a clear soiutionof the digitalis glycosides by filtration of the resultant extract. Chlorophyll was then precipitated at temperatures around 60 C. and was then removed. The aqueous solution-thus obtained was capable of use'as such or could be worked up into pure digital-is glycosides in accordance with known procedures or in accord-- ance with'procesures disclosed in said application.

According to the present invention it' has been found that it is possible to isolate substantially pale dig italis 'glycosides from the aquesus soiuti'on in a very "si niple manner.

It is, therefore, anobject "ofthe present invention to -provide a novel-process of isolating digitalisglycosides frorn' an aqueous solution prepared directly from the plant material.

In carrying out theprese'nt invention it-has been found that the aqueousextract of the digitalis glycosides can be prepared in the same manisclo'sedinm cope mg application. To "end the plant inaterial ontar l g digi-talis gly osid uch as pl-ants either in 'the form of insist ieaves-andot-he plant parts :1 6f -leaves 1'ireisel'ved ast'rreea mg nethods, is naXedwith-w er-arid subjec ted to tlioreugh dis'integration cap "bl-e 6f rupturing ofall--or 1"a;rly' all of th'e pla'ii cells. -"Ihi'sdisriiteg ation may baaccomplished b means'of a dis 't'egrati'ng device-,- such as the Wai-ing Blen'dcr, where relatively small batchesare handled'or a Reitz --Bisi'ntegrator, Type -RD-lB here large loatchesarehandle'd. -The di'sintegration permits the water in which the plant mate'rial -is sus pended while being disintegrated to reac'h II the digital-is. g lyc'osides containedin the plant -cells, and-the digitalis glycosi'des -being' water soluble are transferred to theaqueous mediumwhich is then separated-from the aqueous' mass' of disintegrated plant 'inaterialby filtrationorcentrifugi-ng. Howev'er;=chlorophyl1 #and'other materiaIS, which are L'1nd'esira'ble so far as the digita'lis preparationis concerned, also find their'way into the without "harmful effect by heating the separated aqueous liquor to 'a temperature in thesrange of 60 C. to (2., preferably about '60" C. fora Short period of time. Usually it'is sufiicient just to bring the aqueous liquor up to'temperature. The heating facilitates coagulation and precipitation of the chlorophyll and other undesirable constituents and seems'to'inactivate enzymes. Thereafter, the coagulated chlorophyll andother material which has been rendered insolublemay'be removed by filtration for examplethroughffilter paper or a muslin pad'with or without the addi tion of a filter aid. "The insolubie'undesirahle constituents can also beremoved by'centrifug'ing. As a resultof' this filtration or centrifuging there results a lightamber colored aqueous solution containing practicallyall'of the activeglycosides (digitalis) "originally present in the leaf.

From this aqueous solution thedigitalisglycosides may berecovered invarious wa'ys. "The aqueous solution may be extracted witha water immiscible, low aliphatic ketone solvent, such as methyl ethyl, diethyl, methyl 'propyl; ethyl propyl, methylisobutyl and methyl butyl 'ketones. For purposes of illustration, the invention will be describe'dwith particular reference to methyl isobutyl-ketone; which is the preferredsolvent. 'It is to be understood,"however, that theinvention is not limited thereto.

Afterextraction of the aqueous solution with several quantities of the methyl isobutylketo'ne, the "solvent portions are combined and concentratedto asmall volume. 'At the later stages'of concentration awhite crystalline 'substance'niay separate. Distillation is thenstopped-and" the mixture allowed to cool to room temperature and i stand for-an extended period of time'during which crystallization occurs. Crystals formed by this treatment may be removed by filtration and washed with small quantities of methyl isobutyl ketone. The crystals thus obtained. are in most cases almost 'purewhite. Inothers they may be of varying'shades of yellow. They all give the characteristic Keller-Kiliani color test for the digitalis giycosides.

Further purification of the crystalline glycosides may be accomplished by dissolving the crys talline glycosides in a low aliphaticalcoholic solvent, such as methanol, to which has beenadded some of the ketonic solvents, such as'methyl'isobutyl ketone and a quantityof water. The mixture is agitated and thenallowed to stand for the mixture to separate into two distinct layers. The methyl isobutyl ketone layer contains the purified digitalis glycosides and maybe separated and concentrated under vacuum to a small volume. Bycooling this concentrated extract-to room temperature and allowing it to stand for an extendedperiod-of time, white crystalline digitalis glycosides separate: and may. be removed by filtration and maybe washed with'ismall-quantities'mf methyl isobutyl keton'es. JTh'e crystals thus obtained are almost pure white and give the positive Keller-Kiliani color test that is characteristic of the digitalis glycosides.

From Digitalis lanata a very large quantity of crystals is obtained. From Digitalis latca the results are the same, with the exception that the yields of crystalline material are considerably smaller. With Digitalis parpurea the glycosides obtained are not crystalline but at least 90% of the active glycosides of the plant material are obtained in an amorphous state, as determined by biological assay methods.

Another method of isolating the glycosides is as follows: The aqueous filtrate containing the digitalis glycosides extracted directly from the plant material may be mixed with filter cell and the resultant mixture saturated with a neutral alkali metal salt such as sodium or potassium sulfates or chlorides. This results in the precipitation of the digitalis glycosides and the solid material obtained is composed of a mixture of the filter cell and the glycosides. This moist solid material may then be extracted with one of the above solvents, such as methyl isobutyl ketones, and the solution separated from the solid material. This solution may then be concentrated to a small volume and the light colored crystalline digitalis glycosides crystallized from the concentrated solution at room temperature. The crystals thus obtained after washing with a small quantity of methyl isobutyl ketone are almost pure white in some cases, while in others they are of varying shades of yellow. They give the characteristic Keller-Kiliani color test for the digitalis glycosides. The glycosides precipitated on the filter cell in this manner may be kept in an air dried state for long periods of time, for example over a year, after which they may be moistened and extracted with methyl isobutyl ketone and the same treatment applied for the isolation of the crystalline digitalis glycosides.

In this modified manner of proceeding the same results are obtained with Digitalis lutea through the amounts of crystals obtained are smaller. Likewise, in the case of Digitalis purparea the digitalis glycosides are not obtained in a crystalline form but over 90% of the active glycosides are obtained in an amorphous state, as determined by biological assay methods.

The following examples will serve to illustrate the invention:

Example I One thousand grams of fresh leaves of Digitalis laiiata were disintegrated in portions of about 280 grams each in the presence of 400 cc. of water in the Waring Blender for about is minutes. This product was heated on the steam bath until a temperature of about 70 C. was obtained. This mixture was filtered on a Buchner funnel and the solid mass washed with hot water 80-9? C. A total volume of about 3 liters of aqueous extract was obtained. This aqueous solution was extracted with three 360 cc. portions of methyl isobutyl ketone. The methyl isobutyl ketone portions were combined and concentrated under vacuum to a volume of about 29 cc. During the latter stages of concentration, a white crystalline substan e separated from the methyl isobutyl ketone solution. The distillation was stopped and. the mixture allowed to stand cvernighand to cool to room temperature, whereupon crystals precipitated out. The crystals were removed by filtration and were subsequently washed with a small amount, to 00., of methyl isobutyl ketone. The crystals thus obtained were, in some cases, almost pure white. In others, they were varying shades of yellow. They gave the characteristic Keller-Kiliani color test for the digitalis glycosides.

The first 300 cc. of portion of methyl isobutyl ketone contained most of the crystalline glycosides.

0.5 gram of the crystalline glycosides was dissolved in about 35 cc. of methanol to which was added 350 cc. of methyl isobutyl ketone followed by 350 cc. of water. The mixture was shaken for about one minute and then allowed to stand in a separatory funnel until two distinct layers were obtained. The methyl isobutyl ketone layer was separated and concentrated under vacuum to a small volume, 10 to 20 cc. During the latter stages of this concentration, a white crystalline substance separated from the methyl isobutyl ketone solution. The distillation was halted and the mixture allowed to stand overnight and to cool to room temperature, whereupon crystals formed. The crystals were removed by filtration and were subsequently washed with a small cunt, 19 to 20 cc., of methyl isobutyl ketone. crystals thus obtained were almost pure that is characteristic of the digitalis gly- These crystals melted at 190-219 C. Acng to the US? XIII Cat. Assay Method for cardiac active principles these crystals have it of the cardiac activity of pure digitoxin.

Example I! Digitalis latea was substituted for Digitalis Zaiiata in the procedure of Example I. The same results were obtained with the exception that the yields of crystalline material (glycosides) were considerably smaller. These crystals melted at l-210 C.

Example III Digitalis pu purea was substituted for Digitalis lanata in the procedure of Example I. While no crystalline material was obtained by this procedure, an amorphous residue was obtained. At least 9fi% of the active glycosides in the plant material were obtained in the amorphous state, as determined by biological assay methods.

Example IV One thousand grams of fresh Digitalis lanata leaves were disintegrated and extracted with water in accordance with the procedure of Example I. The product was heated on the steam bath until a temperature of about 70 C. was obtained. This mixture was filtered in the solid mass on a Buchner funnel, washed with hot water at 80-90" C. The aqueous filtrate was mixed with about 200 grams of filter cell and the mixture saturated with sodium sulphate. This mixture was filtered and the solid material was collected on a Buchner funnel. The solid material was divided into two portions while it was still wet. One portion was air dried and the other was shaken with three successive cc. portions of methyl isobutyl ketone. The methyl isobutyl ketone was separated from the solid material. This solution was concentrated under vacuum to a Volume of about 10 cc. During the latter stages of concentration, a white crystalline substance separated from the methyl isobutyl ketone solution. The mixture was allowed to stand overnight at room temperature for further crystallization. The crystals were removed by filtration and were subsequently washed with a small amount, to cc., of methyl isobutyl ketone. I' he crystals thus obtained were in some cases almost pure white. In others they were varying shades of yellow. They gave the characteristic Keller-Kiliani color test for the digitalis glycosides. These crystals melted at 190-210 C.

The air dried portion after storage for a year was moistened with water and treated as described above with the same results.

The same results were obtained with Digitalis Zutea, however, smaller amounts of crystals were obtained.

In the case of Digitalis purpurea, no crystals were obtained, however. about 90 per cent of the acting glycosides were obtained in an amorphous state as determined by biological assay methods.

While various modifications of the invention have been described, it is to be understood that the same is not limited thereto but that other variations may be possible without departing from the spirit thereof.

What I claim is:

1. The process of preparing digitalis glycosides which comprises comminuting plant material containing digitalis and selected from the group consisting of fresh, moist plant material and such material preserved by quick-freezing until at least most of the plant cells containing the digitalis glycosides are ruptured extracting the disintegrated plant material With water to produce a preliminary aqueous extract, heating the preliminary extract to about 60 C. to coagulate the chlorophyll and other undesired constituents, separating insoluble material from the preliminary extract to produce a light colored aqueous extract substantially free from chlorophyll, extracting the aqueous extract with a water immiscible low aliphatic ketone solvent for the digitalis glycosides and separating the digitalis glycosides from the ketone solvent.

2. The process of producing digitalis glycosides which comprises comminuting plant leaves containing digitalis glycosides and selected from the group consisting of fresh, moist leaves and leaves preserved by quick-freezing, extracting the comminuted leaves with water to produce a preliminary aqueous extract, heating the preliminary extract to about 60 C. to coagulate the chlorophyll and other undesired constituents,

separating insoluble material from the crude extract to produce a light colored aqueous extract substantially free from chlorophyll, precipitating glycosides from the aqueous extract by the addi tion of a neutral alkali metal salt, separating the precipitated glycosides from the aqueous extract, extracting the precipitated glycosides with a water immiscible, low aliphatic ketone solvent for the digitalis glycosides and recovering the digitalis glycosides from the ketone solvent.

3. The process of preparing digitalis glycosides which comprises comminuting plant material containing digitalis and selected from the group consisting of fresh, moist plant material and such material preserved by quick-freezing until at least most of the plant cells containing the digitalis glycosides are ruptured, extracting the disintegrated plant material with water to produce a preliminary aqueous extract, heating the preliminary extract to about 60 C. to coagulate the chlorophyll and other undesired constituents, separating insoluble material from the preliminary extract to produce a light colored aqueous extract substantially free from chlorophyll, extracting the aqueous extract with methyl isobutyl ketone to produce a solution of the digitalis glycosides, concentrating the digitalis glycosides solution and recovering digitalis glycosides from said solution.

4. The process of preparing digitalis glycosides which comprises comminuting plant material containing digitalis and selected from the group consisting of fresh, moist plant material and such material preserved by quick-freezing until at least most of the plant cells containing the digitalis glycosides are ruptured, extracting the disintegrated plant material with water to produce a preliminary aqueous extract, heating the preliminary extract to about C. to coagulate the chlorophyll and other undesired constituents, separating insoluble material from the preliminary extract to produce a light colored aqueous extract substantially free from chlorophyll, extracting the aqueous extract with methyl isobutyl ketone to produce a solution of the digitalis glycosides, concentrating the digitalis glycosides solution and crystallizing the digitalis glycosides from the methyl isobutyl ketone solution.

The process according to claim 4 in which the crystalline digitalis glycosides are extracted with a mixture of aqueous methanol and methyl isobutyl ketone and the digitalis glycosides crystallized from the methyl isobutyl ketone solution thus produced.

6. The process according to claim 2 in which the precipitated digitalis glycosides are extracted with methyl isobutyl ketone and the digitalis glycosides are crystallized from the methyl isobutyl ketone solution thus produced.

7. The process of producing digitalis glycosides which comprises comminuting plant leaves containing digitalis glycosides and selected from the group consisting of fresh, moist leaves and leaves preserved by quick-freezing, extracting the comminuted leaves with water to produce a preliminary aqueous extract, heating the preliminary extract to about 60 C. to coagulate the chlorophyll and other undesired constituents, separatinsoluble material from the crude extract to produce a light colored aqueous extract substantially free from chlorophyll, precipitating glycosides from the aqueous extract by the addition of sodium sulfate, separating the precipitated glycosides from the aqueous extract, extracting the precipitated glycosides with a water immiscible, low aliphatic ketone solvent for the digitalis glycosides and recovering the digitalis glycosides from the ketone solvent.

8. The process of producing digitalis glycosides which comprises comminuting plant leaves containing digitalis glycosides and selected from the group consisting of fresh moist leaves and leaves preserved by quick-freezing, extracting the comminuted leaves with water to produce a preliminary aqueous extract, heatin the preliminary extract to about 60 C. to coagulate the chlorophyll and other undesired constituents, separating the insoluble material from the crude extract to produce a light colored aqueous extract sub stantially free of chlorophyll, precipitating digitalis glycosides therefrom by the addition of solid sodium sulfate, separating the precipitated digitalis glycosides from the aqueous extract, ex tracting the precipitated digitalis glycosides with methyl isobutyl ketone and crystallizing the digitalis glycosides from the methyl isobutyl ketone extract.

OLE GISVOLD.

No references cited. 

1. THE PROCESS OF PREPARING DIGITALIS GLYCOSIDES WHICH COMPRISES COMMINUTING PLANT MATERIAL CONTAINING DIGITALIS AND SELECTED FROM THE GROUP CONSISTING OF FRESH, MOIST PLANT MATERIAL AND SUCH MATERIAL PRESERVED BY QUICK-FREEZING UNTIL AT LEAST MOST OF THE PLANT CELLS CONTAINING THE DIGITAILS GLYCOSIDES ARE RUPTURED, EXTRACTING THE DISINTEGRATED PLANT MATERIAL WITH WATER TO PRODUCE A PRELIMINARY AQUEOUS EXTACT, HEATING THE PRELIMINARY EXTRACT TO ABOUT 60*C. TO COAGULATE THE CHLOROPHYLL AND OTHER UNDESIRED CONSTITUENTS, SEPARATING INSOLUBLE MATERIAL FROM THE PRELIMINARY EXTRACT SUBSTANTIALLY FREE FROM CHLOROPHYLL, EXTRACTING THE AQUEOUS EXTRACT WITH A WATER IMMISCIBLE LOW ALIPHATIC KETONE SOLVENT FOR THE DIGITALIS GLYCOSIDES AND SEPARATING THE DIGITALIS GLYCOSIDES FROM THE KETONE SOLVENT. 